Lubricant filled bellows for shafts

ABSTRACT

An extensible and contractable bellows adapted to be mounted about a shaft. The bellows includes a hollow body portion that is substantially cylindrical and unstressed when extended, and also includes a plurality of internal ribs adapted to engage the shaft and form lubricating chambers therebetween. The chambers are filled with a suitable fluid such as oil or air, for lubricating the shaft. A plurality of notched passageways or nibs, formed with the ribs, permits and controls flow of the lubricant between the chambers.

United States Patent Inventors Joe W. Dobklns Fort Worth, Tex.;

l-lalliburton Company, Duncan, Okla. 68,596 Sept. 1, 1970 Sept. 14, 1971 Continuation-impart of application Ser. No. 751,608, Aug. 9, 1968.

Appl. No. Filed Patented LUBRICANT FILLED BELLOWS FOR SHAF'IS 26 Claims, 7 Drawing Figs.

US. Cl 213/43, 213/8 Int. Cl 8613 9/08 Field of Search 213/8, 43; 188/313, 314; 267/64, 65

References Cited I 3 UNITED STATES PATENTS 3,207,324 9/1965 Blake Primary Examiner-Drayton E. Hoffman Attorney-Burns, Doane, Swecker & Mathis 4, 26 t T o 22 I8 1o 64 t 65 L L-v-4. 5S

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ATTORNEYS LUBRICANT FILLED BELLOWS FOR SHAFT S RELATED APPLICATIONS This application is a continuation-in-part of parent application Ser. No. 751,608, filed Aug. 9, 1968, by Joe W. Dobkins for Lubricant-Filled Bellows for Shafts.

BACKGROUND OF THE INVENTION This invention relates to a bellows unit adapted to seal and lubricate a reciprocable shaft. In particular, this invention relates to a lubricant filled bellows sleeve for a piston rod incorporated in a cushioning apparatus for railway cars.

In a piston and cylinder assembly for a railway cushioning apparatus, it has been common practice for many years, to protect the portion of the piston rod that is reciprocable into and out of the cylinder from corrosion by dust and external moisture. Where a seal is employed between the piston rod and the cylinder, it is often desirable to additionally provide for lubrication of the piston rod.

To this end, a flexible bellows sleeve is sometimes mounted about the piston rod of the cushioning apparatus.

At least one priorcushioning apparatus of this type includes an extensible and contractible, convoluted sleeve having one end fixed with respect to the cushioning cylinder and the other end secured to a disc fixed to the piston rod. The bellows sleeve forms a sealed chamber protecting the piston rod from external dust and moisture, and contains a small quantity of lubricating oil for the purpose of lubricating the piston rod. In the prior known device, a spring-closed check valve is provided on the disc on which the bellows is mounted in order that the bellowsmay breathe.

Although prior flexible bellows assemblies of the type described are generally adequate, they may sometimes prove unsatisfactory for a number of reasons. For example, since the bellows defines a single chamber about the rod, the extension or contraction of the bellows may result in the accumulation of the oil in a terminal portion of the chamber, thereby causing large dry spots on the rod. Without discrete lubricating chambers between the bellows and the piston rod along the length thereof, there is a danger that the rod may not be completely or uniformly lubricated where a liquid lubricant is employed. Such uniform lubrication is highly desirable for smooth operation of the piston of a hydraulic cushioning apparatus.

Another disadvantage of the previously described prior structure resides in the fact that no provision is made to control the flow of the lubricant during extension and contraction of the bellows. In the absence of controlled flow, cavitation of the lubricating liquid may occur, and may subject' the bellows to undesirable stretching forces resulting from an increase in volume between the bellows and the piston rod. It is desirable to avoid such stretching in order to prolong the useful life of the bellows.

In this connection, if an attempt were made to use solely a gaseous lubricant such as air in the prior, single chamber bellows, the absence of controlled How might produce zones of vacuum and zones of high pressure that might tend to subject the bellows to undesirable stress conditions.

Although a flexible bellows defining discrete fluid chambers along the length of the piston rod has been employed in a cushioning apparatus for an entirely different purpose (to accommodate the flow of fluid displaced by the volume of the piston rod in arrangements having no seal between the cylinder and the piston rod), such a bellows may prove unsatisfactory as a lubricating bellows for a number of reasons. For example, there is no communication between some of these chambers unless the pressure of the fluid accommodated by the bellows is great enough to lift the chamber walls.

Another disadvantage of a known, prior art discrete chamber bellows stems from the fact thatthe bellows, in its uninstalled relaxed state, is preformed with convoluted chamhas each having a thickened bead section ori the rootportion of the chamber wall for contacting theipistonrod. These convoluted chambers may be difficult and e'xpensive toform by conventional processes,such as molding, because of the rela-" tively complex mold shapes required. Furthermore, formation of the thickened bead portions may necessitate the maintaining of costly. dimensional tolerances.

In. addition, since the relaxed state of thisknown, preconvoluted bellows corresponds approximately to its operationally innermost contracted position, almost all piston movement-results in stresses'tending'to stretch thebellows walls. It would be desirable to avoid such stretching because if may induce cracking or aggravate existing faults.

SUMMARY OF A PREFERRED EMBODIMENT OF THE INVENTION It is therefore a general object of the invention to provide a bellows sleeve for apiston rod intended to obviate or minimize disadvantages of -the.sort previously noted.

It is a particular object of the invention to provide 'a lubricating bellows sleeve for a piston rod so designed that the possibility of nonuniform lubrication of the rod is effectively minimized,

It is a further object of the invention to provide a flexible bellows sleeve for a piston rod of the type having a means for controlling the flow of the lubricant along the rod.

It is a still further object of the invention to provide a draft gear cushioning apparatus including a lubricating bellows sleeve about the piston rod for minimizing the possibility of nonuniform movement of the piston rod into the cylinder.

It is another object of the invention to provide a draft gear cushioning apparatus including an economical lubricating bellows sleeve having an appreciable useful life.

It is still another object of the invention to provide a discrete chamber draft gear lubricating bellows with a relaxed state corresponding substantially to its outermost extended position in order to minimize stretching during operation.

A preferred embodiment of the invention intended to accomplish at least some of the foregoing objects comprises an axially extensible and contractable bellows sleeve adapted to be mounted about a piston rod and to be filled with a lubricant when so mounted. The lubricant may be a gaseous or liquid fluid such as air or oil. The bellows includes a hollow body portion that is substantially cylindrical and unstressed when the bellows is axially extended. Protruding inwardly of the body portion are a plurality of circumferentially extending axially spaced internal ribs. When the bellows is extended, the internal diameters of the ribs engage the piston rod to form a plurality of lubrication chambers between adjacent ribs. These ribs maintain the body portion of the bellows engagement with the piston rod to thereby prevent extensive unlubricated zones along the length of the piston rod. Thus when a liquid lubricant is employed large dry spots along the length of the rod are avoided and when an air lubricant is employed heat generation by extensive area contact and resulting friction between the bellows and the rod are minimized.

In order to accommodate cross flow of lubricant between the lubrication chambers, the ribs are provided with either a series of circumferentially spaced extending notched passageways, or a plurality of circumferentially spaced inwardly projecting nibs. When the nibs are employed, an interference fit between the nibs and the piston rod results in com.- pression of the ribs in the area adjacent the nibs so that the ribs do not engage the shaft inthat area, thereby providing flow paths on. both sides of the nibs.

The notches or nibs in one rib are aligned with the notches or nibs in, the remainder of the ribs so that there may be an even flow between the channels that willenhance uniform lubrication.

Although the exact portion of the bellows which will fold The bellows is fixed at one end to the cylinder and the other end is fixed in sealing engagement with the piston. When an oil lubricant is utilized, before the latter connection is made, the bellows is filled witl'i'a small quantity of oil while in its extended portion. I

If desired, when liquid lubricant is employed, in order to reduce the possibility of damage to the bellows due to overfilling, either initially or because of failure of the seal between the piston rod and the cylinder, a very small hole may be provided in the bellows. The hole is on the order to one ten thousandth of an inch in diameter so that no air flow into the bellows will occur, while escapement of liquid is permitted in an overfilled condition. It will, however be appreciated that the hole or other bleed may normally be dispensed with regardless of the type of lubricant employed.

THE DRAWINGS A bellows unit constructed in accordance with a preferred embodiment of the invention is illustrated in the accompanying drawings in which:

FIG. 1 is a top view of a hydraulic cushioning piston, bellows and cylinder arrangement mounted in a fixed railway sill shown in cross section;

FIG. 2 is a partial cross-sectional view of the piston, bellows and cylinder arrangement shown in FIG. 1 taken along line 2--2 therein; 7

FIG. 3 is a view of the bellows and piston rod in fully extended position with the bellows shown partially in cross section;

FIG. 4 is a cross-sectional view of the bellows shown in FIG. 3 taken along line 44 therein;

FIG. 5 is a cross-sectional view similar to that shown in FIG. 4 showing an alternative embodiment of the bellows;

FIG. 6 is a longitudinal cross section of the bellows shown in FIG. 5 with the shaft removed; and

FIG. 7 is a cross-sectional view of the bellows shown in FIG. 6 taken along line 7-7 therein.

DETAILED DESCRIPTION General Summary Referring to FIG. 1 of the drawings, a lubricant-filled bellows sleeve 2 according to a preferred embodiment of the invention is shown therein in connection with an hydraulic apparatus 4 for railway cars.

The cushioning apparatus includes a stationary sill 6 attached to the underside of a railway car (not shown). Slidably mounted in the sill 6 is a cylinder housing 8. The bellow sleeve 2, having a cylindrical form in its unstressed condition, is mounted about a piston rod 10. This rod 10 is fixed relative to the sill 6 by means of a spherical bearing" assembly 12 and cooperating fixed bearing plates 14 and 16 (see FIG. 2).

The bellows sleeve 2 comprises an axially extensible and contractable flexible hollow body portion 18 and a plurality of circumferentially extending, axially spaced internal ribs 20 protruding inwardly of the body portion (FIG. 3). The ribs 20 engage the piston rod 10 to form a plurality of spaced, discrete lubricating chambers, as indicated at 22, between adjacent ribs. A suitable lubricant such as air or oil is provided in these chambers 22.

Since fluid communication between the lubricating cham bers 22 is desired, each of the ribs is provided with a plurality of communication ports hereinafter. more fully described.

A first sealing assembly 24 secures one end 26 of the be]- lows sleeve to the movable cylinder housing 8 and the other end 28 of the bellows is sealingly attached to the fixed piston rod 10 by second sealing assembly 30 (FIG. 3). Thus, the sleeve is axially extensible (FIG. 3) and contractable in response to the cushioning sliding movement of the cylinder housing 8 in the stationary sill 6.

Detailed Structure Mounted within the previously mentioned movable housing 8 is a cylinder 32 which slidably receives a fixed cantilever piston 34. This piston 34 is attached to the piston rod 10 (FIG.

2). Reference may be had to U.S. Pat. No. 2,944,681 to W. T. Blake, for further details of a fixed cantilever piston, and movable cylinder assembly conventionally used in railway draft appliances. However, the bellows sleeve 2 is equally suitable for use with a cushioning apparatus having a fixed cylinder and movable piston, or for use with any mechanical movement wherein lubrication of a relatively reciprocable shaft is desired. l

The rear end of the cylinder housing 8 is closed by a cover plate 36 and a shaft sealing bushing 38 and seal assembly 40 which may be of the type shown in US. Pat. Nol 3,30l,4l0 to O. E. Seay.

A suitable restoring mechanism (not shown), of the kind I more particularly described in US. Pat. No. 3,233,747 to Abott et al., may be employed for returning the railway draft appliance to its neutral position following displacement.

In the preferred embodiment, the entire bellows sleeve 2, including the previously mentioned body portion 18 and ribs 20, is unitarily molded of a suitable flexible material such as a rubber compound. It has been found that the rubber compound 320-60 BUNA-N is particularly advantageous because it retains flexible characteristics at high and low temperatures.

In order to minimize the possibility of stretching of the bellows sleeve 2 during operation of the cushioning apparatus 4, the sleeve is molded in a state substantially corresponding to its operationally outermost extended position (FIG. 3), wherein the body portion 18 is substantially cylindrical. In this state, the bellows wall is unstressed so that there is a minimum tendency to cause cracking of the bellows wall during the relative motion of the piston rod 10 between its innermost and ou'-. termost positions.

It will be appreciated that prior art bellows which are preformed with convolutions in a state corresponding approximately to their operationally innermost positions, will be subject to stretching forces during most of the outward movement of the piston rod.

In the extended position of the bellows sleeve 2, the ribs 20 are so dimensioned as to engage the piston rod 10 in a slight interference fit as indicated at 42 (FIGS. 4 and 5). The interference fit thereby insures the discrete nature of the previously mentioned lubricating chambers 22.

The ribs 20 provide rigidity of the bellows sleeve a induce the folding of sleeve during contraction while obviating the need for preforming the sleeve with convolutions. Uniform axial spacing of the ribs along the length of the body portion 18 contributes to more uniform folding of the bellows, thereby minimizing undesirable nonuniform fluid effects.

The previously mentioned communication ports between the chambers 38 may be provided by a plurality of circumferentially spaced, longitudinally extending notched passageways 44 in each of the ribs 20 (FIG. 4).

In an alternative embodiment (FIG. 7), communication between the chambers 20 is provided by a plurality of circumferentially spaced, inwardly projecting nibs 46 on each of the ribs 20. When the bellows sleeve 2 is mounted about the piston rod 10, the nibs 46 engage the piston rod in an interference fit (FIG. 5). The interference fit between the nibs and the piston rod produces a compression of the ribs 20 in the area adjacent the nibs so that the ribs are lifted from the piston rod in that vicinity. Compression and resultant lifting of the ribs brings about the formation of generally V-shaped flow passages 48 on both sides of the nibs The interference fit between the nibs and the shaft or piston rod 10 causes the body portion 18 of the bellows sleeve to bulge slightly, as indicated at 50.

Although the lubricating chambers 22 aid in maintaining uniform lubrication of the piston rod 10, it will be appreciated that the communication ports provided by the notched passageways 44 or nibs 46 further provide such uniform lubrication by controlling the flow of fluid between the chambers.

Furthermore, the ports minimize the possibility of stretching of the bellows which may result from uncontrolled flow of the lubricant. Uniform circumferential spacing of the communication ports, and longitudinal alignment between the ports associated with each rib, as illustrated, enhances operation of the bellows unit in that a deep, even flow between the lubrication chambers is provided so that possible turbulence effects, vacuum effects (with an air lubricant) and cavitation (with a liquid lubricant) are substantially avoided.

The previously mentioned seal assembly 24, which fixes the sleeve 2 to the cylinder housing 8, comprises an annular retainer member 50 that is tightly mounted about the body portion of the sleeve adjacent a radially outwardly projecting annular flange 52 (FIG. 6) located at the forward terminal section 26 of the bellows sleeve. The retainer member 50 forces the flange 52 into sealing engagement with the housing and is secured to the housing by suitable retaining means such as the screws 54 and 56.

The previously mentioned seal assembly 28, which fixes the sleeve 2 to the piston rod 10, comprises an annular retaining member 58 that is mounted about the rearmost section 28 of the body portion of the bellows. The retaining member 58 is sealingly secured to the piston rod 10 by spot welding or the like. When liquid lubricant is employed it will be appreciated that such securing is preceded by filling the bellows with the liquid.

It will be appreciated that the oil received in the bellows prevents oxidation of the piston rod 10 and provides a lubricated shaft which substantially minimizes galling and excessive seal wear. However, air as the sole lubricant also provides for smooth operation of the system.

If the seals become worn or if the bellows is overfilled with a liquid lubricant so that it may be damaged in operation, a very small hole (not shown) may be provided in the bellows adjacent the retainer member 58. The hole is on the order of one ten-thousandth of an inch so that the inflow of air to the bellows chambers is inhibited, but the escapement of fluid in the event of an overfilled bellows condition is permitted. As earlier mentioned, the hole may, however, be dispensed with regardless of the type of lubricant employed.

As best viewed in FIG. 6, the end of bellows on which the retainer member 58 is received may be enlarged internally, as indicated at 60 to be received in a corresponding annular channel 62 (FIGS. 2 and 3) formed on the rod 10. On opposite ends of the enlarged bellows portion, annular projections 64 and 66, each extending radially outwardly from the outer bellows periphery, may be provided. The longitudinally innermost one of these projections 64 is rounded and functions to absorb impact between the bellows and the retainer member 58 during contraction of the bellows as well as to minimize the possibility of that member 58 slicing or cutting the bellows in use. The other projection 66 overlies the piston rod portion adjacent the channel 62 and serves as a retainer.

OPERATION AND METHOD OF ASSEMBLY To assemble the bellows unit of the present invention in a hydraulic cushioning apparatus, the cushioning apparatus is first assembled, with the exception of the bellows sleeve and the alignment member 12 of the piston rod.

The front retainer member 50 is then mounted over the flanged end 52 of the bellows, after which the bellows and retainer member are placed over the piston rod 10 in a position for the retainer member to be secured in fluidtight relationship to the cylinder housing 8.

The shaft or rod I0 is then moved to its outermost extended position at which time the bellows is filled with liquid if a liquid lubricant is utilized, care being taken to avoid overfilling of the bellows.

The front retainer member 58 is placed over the front end 28 of the bellows and spot welded or otherwise secured in sealing engagement with the piston rod. Alignment member 12 and the retainer plates 14 and 16 may then be attached to complete the assembly.

During cushioning movement of the cylinder housing 8, the bellows sleeve 2 will fold and unfold between its axially outermost extended position (FIG. 3) and its axially innermost contracted position (FIG. 2). The portion of the piston rod 10 that moves into and out of the cylinder housing is protected from corrosion by dust and external moisture and operates smoothly during cushioning movement because of the uniform lubrication provided by the bellows sleeve.

SUMMARY OF ADVANTAGES It will be seen that following the present invention, a bellows sleeve which is particularly effective in a railway hydraulic cushioning apparatus is provided.

Of particular significance is the provision of discrete lubricating chambers along the length of the piston rod.

Also of importance in this connection is the provision of communication ports between the discrete lubricating chambers. Since these ports control the flow of lubricating fluid, there is little danger of undesirable stretching of the bellows because of turbulence, vacuum or cavitation effects.

Other advantages are provided by the uniform spacing of the rib members forming the chambers, and the uniform spacing of the flow passageways between the chambers.

Furthermore, stretching of the bellows wall is minimized by constructing the bellows in such a way that the outer wall is substantially cylindrical and unstressed in its outermost extended position; thereby miiomizing any tendency to open cracks in the wall during operation.

Although the invention has been described with reference to the embodiments illustrated, it will be appreciated by those skilled in the art that additions, modifications, substitutions, deletions and other changes not specifically described may be made which fall within the spirit of the invention as defined in the following claims.

What is claimed is:

1. In combination with a housing and a shaft telescopingly reciprocable with respect to the housing, an axially extensible and contractable bellows mounted about said shaft, and means for connecting opposite end portions of the bellows respectively to said shaft and said housing; the bellows compI'ISlI'lgZ a hollow body portion, said body portion being substantially cylindrical and unstressed when said bellows is in its axially extended position;

a plurality of circumferentially extending, axially spaced, in-

ternal ribs protruding inwardly of said body portion, said ribs engaging said shaft to form a plurality of discrete lubrication chambers between adjacent ones of said ribs;

means providing lubricant in said lubrication chambers;

and,

said discrete lubrication chambers cooperating to provide substantially uniform lubrication along the shaft.

2. The combination as defined in claim I, the bellows including:

means defining communication ports between each of said lubrication chambers.

3. The combination as defined in claim 2 wherein said means defining said communication ports comprises:

a plurality of circumferentially spaced, longitudinally extending notched passageways in each of said ribs.

4. The combination as defined in claim 3 wherein:

said notched passageways in each one of said ribs are longitudinally aligned with said notched passageways in the remainder of said ribs.

5. The combination as defined in claim 2 wherein said means defining communication ports comprises:

a plurality of circumferentially spaced, inwardly projecting nibs on each of said ribs.

6. The combination as defined in claim 4 wherein:

said nibs on each one of said ribs are longitudinally aligned with said nibs on the remainder of said ribs.

7. The combination as defined in claim 2 and including:

a bleed aperture in said bellows.

8. The combination as defined in claim 2 wherein:

the internal diameter of each of said ribs is such that said bellows is in interference fit with the shaft when said bellows is in its axially extended position.

9. The combination as defined in claim 8 wherein:

the axial spacing between adjacent ribs is substantially the same, thereby tending to induce uniform folding of said bellows.

10. The combination as defined in claim 2 wherein:

said ribs and said body portion are integral.

1 1. A draft gear cushioning apparatus comprising:

a cylinder having a closed end and an open end;

a piston slidably mounted in said cylinder for relative movement with respect thereto;

a piston rod for said piston, at least a portion of said piston rod being movable into and out of said cylinder through said open end;

an axially extensible and contractable lubricant filled bellows mounted about said piston rod for lubricating said portion of said piston rod;

means fixedly mounting one end of said bellows with respect to said cylinder;

means fixedly mounting the other end of said bellows in sealing engagement with said piston rod;

said bellows comprising:

a foldable body portion, said body portion being substantially cylindrical and unstressed when said bellows is axially extended,

a plurality of circumferentially extending longitudinally spaced, internal ribs protruding from said body portion,

said ribs engaging said piston rod and, together with said piston rod, forming a plurality of discrete lubrication chambers,

said discrete lubrication chambers cooperating to provide substantially uniform lubrication along said portion of said piston rod; and

means defining communication ports between each of said lubrication chambers.

12. A cushioning apparatus according to claim 12 wherein:

said communication ports are defined by a plurality of circumferentially spaced notched passageways in each of said ribs said notched passageways in each of said ribs being longitudinally aligned.

13. A cushioning apparatus according to claim 12 wherein:

said communication ports are defined by a plurality of circumferentially spaced inwardly projecting nibs on each of said ribs, said nibs on each of said ribs being longitudinally aligned, and

said piston rod engaging said nibs in interference fit.

14. In combination with a housing and a shaft telescopingly reciprocable with respect to the housing, an axially extensible and contractable lubricating bellows seal mounted about said shaft, and means for connecting opposite end portions of the bellows respectively to said shaft and said housing; the bellows comprising:

a hollow body portion;

said body portion being substantially cylindrical and unstressed when said bellows is axially extended,

means projecting inwardly from said body portion and engaging said shaft for forming a plurality of discrete lubrication chambers,

said discrete lubrication chambers cooperating to provide substantially uniform lubrication along said shaft, and

means for establishing communication between said lubrication chambers.

15. The combination according to claim 15 wherein the bellows includes:

bleed means for preventing overfill of said bellows.

16. In combination with a housing and a shaft telescopingly reciprocable with respect to the housing, an axially extensible and contractable bellows mounted about said shaft, and means for connecting opposite end portions of the bellows respectively to said shaft and said housing; the bellows comrisin p a h llow body portion, said body portion being substantially cylindrical when said bellows is in its axially extended position;

a plurality of circumferentially extending, axially spaced, in ternal ribs protruding inwardly of said body portion, said ribs engaging said shaft to form a plurality of discrete lubrication chambers between adjacent ones of said ribs;

means providing lubricant in said lubrication chambers; and

said discrete lubrication chambers cooperating to provide substantially uniform lubrication along the shaft.

17. An axially extensible and contractable bellows adapted to be connected at opposite end portions to a housing and to a shaft about which the bellows is mounted and which is telescopingly reciprocable with respect to the housing, the bellows being adapted to be filled with a lubricant when so mounted, the bellows comprising:

a hollow body portion, said body portion being substantially cylindrical when said bellows is in its axially extended position;

a plurality of circumferentially extending, axially spaced, in-

ternal ribs protruding inwardly of said body portion;

said ribs being engageable with the shaft and maintaining said body portion out of engagement with the shaft to form a plurality of discrete lubrication chambers between adjacent ones of said ribs when said bellows is mounted about the shaft.

18. A bellows unit as defined in claim 18 including:

means defining communication ports between each of said lubrication chambers when said bellows is mounted about the shaft.

19 A bellows unit as defined in claim 19 wherein said means defining said communication ports comprises:

a plurality of circumferentially spaced, longitudinally extending notched passageways in each of said ribs.

20. A bellows unit as defined in claim 20 wherein:

said notched passageways in each one of said ribs are longitudinally aligned with said notched passageways in the remainder of said ribs.

21. A bellows unit as defined in claim 19 wherein said means defining communication ports comprises:

a plurality of circumferentially spaced, inwardly projecting nibs on each of said ribs.

22. A bellows unit as defined in claim 21 wherein:

said nibs on each one of said ribs are longitudinally aligned with said nibs on the remainder of said ribs.

23. A bellows unit as defined in claim 19 including:

said hollow body portion is substantially unstressed in its axially extended position.

24. A bellows unit as defined in claim 19 wherein:

the internal diameter of each of said ribs is such that said bellows is in interference fit with the shaft when said bellows is in its axially extended position.

25. A bellows unit as defined in claim 25 wherein:

the axial spacing between adjacent ribs is substantially the same, thereby tending to induce uniform folding of said bellows.

26. A bellows unit as defined in claim 19 wherein:

said ribs and said body portion are integral. 

1. In combination with a housing and a shaft telescopingly reciprocable with respect to the housing, an axially extensible and contractable bellows mounted about said shaft, and means for connecting opposite end portions of the bellows respectively to said shaft and said housing; the bellows comprising: a hollow body portion, said body portion being substantially cylindrical and unstressed when said bellows is in its axially extended position; a plurality of circumferentially extending, axially spaced, internal ribs protruding inwardly of said body portion, said ribs engaging said shaft to form a plurality of discrete lubrication chambers between adjacent ones of said ribs; means providing lubricant in said lubrication chambers; and, said discrete lubrication chambers cooperating to provide substantially uniform lubrication along the shaft.
 2. The combination as defined in claim 1, the bellows including: means defining communication ports between each of said lubrication chambers.
 3. The combination as defined in claim 2 wherein said means defining said communication ports comprises: a plurality of circumferentially spaced, longitudinally eXtending notched passageways in each of said ribs.
 4. The combination as defined in claim 3 wherein: said notched passageways in each one of said ribs are longitudinally aligned with said notched passageways in the remainder of said ribs.
 5. The combination as defined in claim 2 wherein said means defining communication ports comprises: a plurality of circumferentially spaced, inwardly projecting nibs on each of said ribs.
 6. The combination as defined in claim 4 wherein: said nibs on each one of said ribs are longitudinally aligned with said nibs on the remainder of said ribs.
 7. The combination as defined in claim 2 and including: a bleed aperture in said bellows.
 8. The combination as defined in claim 2 wherein: the internal diameter of each of said ribs is such that said bellows is in interference fit with the shaft when said bellows is in its axially extended position.
 9. The combination as defined in claim 8 wherein: the axial spacing between adjacent ribs is substantially the same, thereby tending to induce uniform folding of said bellows.
 10. The combination as defined in claim 2 wherein: said ribs and said body portion are integral.
 11. A draft gear cushioning apparatus comprising: a cylinder having a closed end and an open end; a piston slidably mounted in said cylinder for relative movement with respect thereto; a piston rod for said piston, at least a portion of said piston rod being movable into and out of said cylinder through said open end; an axially extensible and contractable lubricant filled bellows mounted about said piston rod for lubricating said portion of said piston rod; means fixedly mounting one end of said bellows with respect to said cylinder; means fixedly mounting the other end of said bellows in sealing engagement with said piston rod; said bellows comprising: a foldable body portion, said body portion being substantially cylindrical and unstressed when said bellows is axially extended, a plurality of circumferentially extending longitudinally spaced, internal ribs protruding from said body portion, said ribs engaging said piston rod and, together with said piston rod, forming a plurality of discrete lubrication chambers, said discrete lubrication chambers cooperating to provide substantially uniform lubrication along said portion of said piston rod; and means defining communication ports between each of said lubrication chambers.
 12. A cushioning apparatus according to claim 12 wherein: said communication ports are defined by a plurality of circumferentially spaced notched passageways in each of said ribs said notched passageways in each of said ribs being longitudinally aligned.
 13. A cushioning apparatus according to claim 12 wherein: said communication ports are defined by a plurality of circumferentially spaced inwardly projecting nibs on each of said ribs, said nibs on each of said ribs being longitudinally aligned, and said piston rod engaging said nibs in interference fit.
 14. In combination with a housing and a shaft telescopingly reciprocable with respect to the housing, an axially extensible and contractable lubricating bellows seal mounted about said shaft, and means for connecting opposite end portions of the bellows respectively to said shaft and said housing; the bellows comprising: a hollow body portion; said body portion being substantially cylindrical and unstressed when said bellows is axially extended, means projecting inwardly from said body portion and engaging said shaft for forming a plurality of discrete lubrication chambers, said discrete lubrication chambers cooperating to provide substantially uniform lubrication along said shaft, and means for establishing communication between said lubrication chambers.
 15. The combination according to claim 15 wherein the bellows includes: bleed means for preventing overfill of said bellows.
 16. In combination with a housing and a shaft telescopingly reciprocable with respect to the housing, an axially extensible and contractable bellows mounted about said shaft, and means for connecting opposite end portions of the bellows respectively to said shaft and said housing; the bellows comprising: a hollow body portion, said body portion being substantially cylindrical when said bellows is in its axially extended position; a plurality of circumferentially extending, axially spaced, internal ribs protruding inwardly of said body portion, said ribs engaging said shaft to form a plurality of discrete lubrication chambers between adjacent ones of said ribs; means providing lubricant in said lubrication chambers; and said discrete lubrication chambers cooperating to provide substantially uniform lubrication along the shaft.
 17. An axially extensible and contractable bellows adapted to be connected at opposite end portions to a housing and to a shaft about which the bellows is mounted and which is telescopingly reciprocable with respect to the housing, the bellows being adapted to be filled with a lubricant when so mounted, the bellows comprising: a hollow body portion, said body portion being substantially cylindrical when said bellows is in its axially extended position; a plurality of circumferentially extending, axially spaced, internal ribs protruding inwardly of said body portion; said ribs being engageable with the shaft and maintaining said body portion out of engagement with the shaft to form a plurality of discrete lubrication chambers between adjacent ones of said ribs when said bellows is mounted about the shaft.
 18. A bellows unit as defined in claim 18 including: means defining communication ports between each of said lubrication chambers when said bellows is mounted about the shaft. 19 A bellows unit as defined in claim 19 wherein said means defining said communication ports comprises: a plurality of circumferentially spaced, longitudinally extending notched passageways in each of said ribs.
 20. A bellows unit as defined in claim 20 wherein: said notched passageways in each one of said ribs are longitudinally aligned with said notched passageways in the remainder of said ribs.
 21. A bellows unit as defined in claim 19 wherein said means defining communication ports comprises: a plurality of circumferentially spaced, inwardly projecting nibs on each of said ribs.
 22. A bellows unit as defined in claim 21 wherein: said nibs on each one of said ribs are longitudinally aligned with said nibs on the remainder of said ribs.
 23. A bellows unit as defined in claim 19 including: said hollow body portion is substantially unstressed in its axially extended position.
 24. A bellows unit as defined in claim 19 wherein: the internal diameter of each of said ribs is such that said bellows is in interference fit with the shaft when said bellows is in its axially extended position.
 25. A bellows unit as defined in claim 25 wherein: the axial spacing between adjacent ribs is substantially the same, thereby tending to induce uniform folding of said bellows.
 26. A bellows unit as defined in claim 19 wherein: said ribs and said body portion are integral. 